Vehicle With Cabin

ABSTRACT

A vehicle with a cabin comprises a vehicle body supported by a plurality of wheels; a cabin bracket supported by the vehicle body; an elastic member for supporting the cabin, disposed between the cabin and the cabin bracket; and a weight member attached to a plate-shaped member of the cabin.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/051,812, filed on Mar. 19, 2008, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle with a cabin, in which thecabin is supported by a vehicle body.

2. Description of the Related Art

As disclosed in JP 2002-356184, for example, a vehicle with a cabin isknown as a conventional technique in which an acoustic absorbent sheetis provided to the floor, the ceiling wall, and other parts of thesteering unit of the cabin so as to reduce noise inside the cabin.

In the vehicle with a cabin disclosed in the above reference, aconfiguration is adopted in which the in-cabin noise is transmitted toan acoustic absorbent material via a plurality of holes formed in thesurface of the acoustic absorbent sheet, and noise inside the cabin isreduced through the sound-absorbing effects of the acoustic absorbentmaterial. However, the noise inside the cabin is not reduced by reducingvibration transmitted from the vehicle body to the floor surface,ceiling walls, and other parts of the steering unit. As a result, evenwhen the acoustic absorbent sheet is provided to the floor, ceilingwalls, and other parts of the steering unit, not only are thenoise-reducing effects minimal for the surface area in which theacoustic absorbent sheet is affixed or provided, but noise inside thecabin cannot be adequately reduced, and noise caused by vibration thatis transmitted from the vehicle body to the floor, ceiling walls, andother parts of the steering unit contributes significantly to in-cabinnoise, which continues to cause discomfort to the operator.

In the vehicle with a cabin disclosed in the abovementioned reference, aconfiguration is adopted in which noise inside the cabin is reduced byaffixing or providing an acoustic absorbent sheet having a wide surfacearea over a wide range that includes the floor, ceiling walls, and otherparts of the steering unit. As a result, drawbacks occur in that thecost of the acoustic absorbent sheet increases; the manufacturing costof the vehicle markedly increases; a large amount of time is required toaffix or provide the acoustic absorbent sheet to the floor, ceilingwalls, and other parts of the steering unit; and the productivity ofassembling the vehicle is adversely affected.

Therefore, a reinforcing member, a steel plate for suppressingvibration, or the like may be attached to the floor, ceiling walls, andother parts of the steering unit to reduce vibrations transmitted fromthe vehicle body to the floor, ceiling walls, and other parts of thesteering unit, and to reduce the in-cabin noise that is uncomfortable tothe operator. However, when a reinforcing member, a steel plate forsuppressing vibration, or the like is attached to the floor, ceilingwalls, and other parts of the steering unit, drawbacks occur in that themanufacturing cost of the vehicle markedly increases, and the weight ofthe vehicle increases in conjunction with attaching the reinforcingmember, the steel plate for suppressing vibration, or the like.

As disclosed in JP 8-142776, a soundproofing structure for a vehicle isknown as another conventional technique in which an acoustic absorbentmaterial is provided between an inner lining material and a door body sothat noise inside the cabin can be reduced by the door.

In the vehicle soundproofing structure according to JP 8-142776, aconfiguration is adopted in which the acoustic absorbent material ishoused inside the inner lining material, noise that penetrates into thedoor body from the joint or the like between the inner lining materialand the door body is transmitted to the acoustic absorbent material, andthe noise inside the cabin can be reduced, but the in-cabin noise isabsorbed by the inner lining material, and is less likely to betransmitted to the acoustic absorbent material. As a result, the noisethat occurs inside the cabin is less likely to be absorbed by theacoustic absorbent material, and there is room for improvements to bemade to reduce the noise inside the cabin.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome at least one of thedrawbacks of the prior art as described above.

The vehicle with a cabin according to the present invention comprises avehicle body supported by a plurality of wheels; a cabin bracketsupported by the vehicle body; an elastic member for supporting thecabin, disposed between the cabin and the cabin bracket; and a weightmember attached to a plate-shaped member of the cabin.

Through such a configuration, when noise from the vehicle body istransmitted to the cabin via the elastic member, the relativelynon-rigid plate-shaped member is vibrated by the vibration from thevehicle body, and the vibration transmitted to the plate-shaped membercan be reduced by the weight effects of the weight member that isattached to the plate-shaped member. As a result, in-cabin noise causedby the vibration transmitted from the vehicle body to the plate-shapedmember can be reduced, and the in-cabin noise can be efficientlyreduced.

In one aspect of the present invention, the plate-shaped member ispreferably one of a rear wheel fender and a floor panel of the cabin.

In one aspect of the present invention, the weight member is preferablyattached to the plate-shaped member by a bolt via a rubber isolator.

In one aspect of the present invention, a cylindrical member that is incontact with the plate-shaped member is preferably provided between theweight member and the bolt.

In one aspect of the present invention, the weight member is preferablyprovided such that attachment of the weight member moves a peak of avibration acceleration as a function of frequency in a direction of lowfrequency.

The vehicle with a cabin according to the present invention comprises: avehicle body that is supported by a plurality of wheels and thatsupports the cabin; an openings portion in which a plurality of openingsis formed and which is provided to a portion of an inside surface of thecabin; and an acoustic absorbent material disposed on an inner surfaceof the inside surface provided with the openings portion.

Through such a configuration, noise inside the cabin is transmitted tothe acoustic absorbent material disposed toward the inner surface of theinside surface through the plurality of openings formed in the openingsportion, and the noise is absorbed by the sound-absorbing effects of theacoustic absorbent material. As a result, the in-cabin noise is easilytransmitted to the acoustic absorbent material from the plurality ofopenings formed in the openings portion, the in-cabin noise is easilyabsorbed by the acoustic absorbent material, and the in-cabin noise canbe efficiently reduced.

In one aspect of the present invention, the openings portion ispreferably formed in a pillar of a cabin frame that constitutes thecabin.

The openings portion provided with the acoustic absorbent material canthereby be placed in a high position inside the cabin, and the acousticabsorbent material can be disposed at a height that is near the ears ofthe operator seated in the operating seat. As a result, noise at aheight near the ears of the operator seated in the operating seat can beefficiently absorbed by the acoustic absorbent material.

In one aspect of the present invention, the openings portion ispreferably formed at a rear part of an inner roof of the cabin.

In one aspect of the present invention, each of the plurality ofopenings preferably has a diameter of 5 mm or less, and verticallyadjacent openings are preferably arranged horizontally staggered fromeach other.

In one aspect of the present invention, the openings portion ispreferably formed in the pillar provided to a side of an operating seatprovided inside the cabin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left side view showing the entire tractor;

FIG. 2 is a transverse sectional plan view showing the structure of thecabin;

FIG. 3 is a left side view showing the structure of the cabin;

FIG. 4 is a longitudinal sectional back view showing the vicinity of thecabin bracket;

FIG. 5 is a longitudinal sectional side view showing the vicinity of thedynamic damper of the floor panel;

FIG. 6 is a longitudinal sectional back view showing the vicinity of thedynamic damper of the floor panel;

FIG. 7 is a back view showing the vicinity of the dynamic damper of therear wheel fender;

FIG. 8 is a longitudinal sectional side view showing the vicinity of thedynamic damper of the support bracket;

FIG. 9 is a rough plan view showing the method for setting theattachment position of the dynamic damper;

FIG. 10 is a rough view in which a floor panel or the like is modeled;

FIG. 11 is a graph showing an example of the results of measuring thevibration acceleration of each frequency in the floor panel;

FIG. 12 is a graph showing an example of the results of measuring thenoise for each frequency when the dynamic damper is mounted to the floorpanel;

FIG. 13 is a graph showing an example of the results of measuring thevibration acceleration for each frequency in the rear wheel fender;

FIG. 14 is a graph showing an example of the results of measuring thenoise for each frequency when the dynamic damper is mounted to the rearwheel fender;

FIG. 15 is a graph showing an example of the results of measuring thevibration acceleration for each frequency in the support bracket;

FIG. 16 is a graph showing an example of the results of measuring thenoise for each frequency when the dynamic damper is mounted to thesupport bracket;

FIG. 17 is a table comparing the results of measuring the noise for eachattachment position;

FIG. 18 is a left side view showing the entire tractor;

FIG. 19 is a transverse sectional plan view showing the structure of thecabin interior;

FIG. 20 is a perspective view showing the structure in the vicinity ofthe center pillar;

FIG. 21 is a longitudinal sectional front view showing the structure inthe vicinity of the center pillar;

FIG. 22 is a transverse sectional plan view showing the structure of thevicinity of the center pillar;

FIG. 23 is a perspective view showing the detailed structure of theopenings portion;

FIG. 24 is a perspective view showing the structure of the inner roofrear part;

FIG. 25 is a graph showing an example of the results of measuring thenoise for each frequency;

FIG. 26 is a table comparing the results of measuring the noise for eachattachment position;

FIG. 27 is a perspective view showing the structure of the openingsportion and the acoustic absorbent material in a first modification ofthe present invention;

FIG. 28 is a transverse sectional plan view showing the structure of theopenings portion and the acoustic absorbent material in a firstmodification of the present invention; and

FIG. 29 is a rough plan view of the inside of the cabin when the floorsheet is installed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Multiple embodiments will be described in the present specification.Combinations of the characteristics of one embodiment with thecharacteristics of another embodiment are encompassed by the scope ofthe present invention.

Embodiment 1

An embodiment relating to the dynamic damper will first be described.

[Overall Structure of the Tractor]

The overall structure of the tractor as an example of the vehicle with acabin will be described based on FIGS. 1 through 4. FIG. 1 shows a sideview of the entire tractor, and FIGS. 2 and 3 are a transverse sectionalplan view and a side view, respectively, of the cabin 8. FIG. 4 is atransverse sectional back view showing the vicinity of the cabin bracket30.

As shown in FIGS. 1 through 3, the tractor is configured according to afour-wheel-drive specification in which a pair of left and right frontwheels 1 that can steer and drive, as well as a pair of left and rightrear wheels 2, are provided to a vehicle body 3. A hood part 5 in whichan engine 4 and other components are housed is provided at the front ofthe vehicle body 3; and a cabin 8 in which a steering handle 6, anoperating seat 7, and other components are housed is provided at therear of the vehicle body 3.

A front frame 10 extends forward from the lower part of the engine 4,and an axle case or the like (not shown) for mounting the front wheels 1is supported by the front frame 10. A clutch housing 11 extends to therear from the engine 4, a transmission case 12 positioned below theoperating seat 7 is connected to the clutch housing 11, and the driveforce from the engine 4 is transmitted to the rear wheels 2.

A link mechanism 13 and a power take-off shaft 14 composed of a pair ofleft and right lift arms are provided at the rear of the vehicle body 3;a rotary cultivator or the like (not shown) is connected to the linkmechanism 13 so as to be capable of being raised and lowered; and therotary cultivator or the like can be raised, lowered, and driven byconnecting the rotary cultivator or the like to the power take-off shaft14.

The cabin 8 is composed of a cabin frame 20, a front glass 16 forcovering the front surface of the cabin frame 20, doors 17 capable ofpivoting open and closed that are provided to the entrances on bothsides of the cabin frame 20, side glasses 18 provided to the rear partsof the doors 17, and a rear glass 19 for covering the rear surface ofthe cabin frame 20.

The cabin frame 20 is provided with an angled pipe support frame 21 forsupporting the cabin 8, and a lower frame 22 connected to the supportframe 21. A pair of left and right front pillars 23, a pair of left andright center pillars 24, and a pair of left and right rear pillars 25extend upward from the front end, the center part, and the rear end,respectively, of the lower frame 22; and the front pillars 23, thecenter pillars 24, and the rear pillars 25 are each connected to anupper frame 26. The various frames constituting the cabin frame 20 areformed by welding and molding pipe materials or the like.

The upper part of the cabin frame 20 is covered from above by an outerroof 27 that is formed hollow by a blow molded resin, and the outer roof27 is fixed to the upper frame 26 via a seal member (not shown).

A floor panel 28 (corresponds to the plate-shaped member) for formingthe floor of the cabin 8 is connected to the lower part of the cabinframe 20, and an operating seat 7 is provided at the rear center of thefloor panel 28. Angled pipe front-rear frames 15 elongated to the frontand rear are fixed to the left and right sides of the lower surface sideof the floor panel 28, the distal end parts of the front-rear frames 15are fixed to brackets 41 described hereinafter, and the rear end partsof the front-rear frames 15 are fixed to support brackets 44.

Rear-wheel fenders 29 positioned on the left and right sides of thecabin 8 are fixed to the lower part of the lower frame 22, and therear-wheel fenders 29 are composed of a fender body 29A shaped so as tocover the external peripheral parts of the rear wheels 2 from above, anda plate 29B positioned to the inside of the rear wheels 2.

The front glass 16 is fixed across the left and right front pillars 23that form the cabin frame 20, and the front surface of the cabin frame20 is covered by the front glass 16. The rear glass 19 is attachedacross the left and right rear pillars 25 that form the cabin frame 20,and the rear surface of the cabin frame 20 is covered by the rear glass19.

The doors 17 are attached so as to be able to pivot open and closedabout the axes of the rear end parts in the entrances on both sides ofthe cabin frame 20 formed between the front pillars 23 and the centerpillars 24, and side glasses 18 are attached so as to be able to pivotopen and closed between the center pillars 24 and the rear pillars 25.

The left and right sides of the front part of the cabin 8 are supportedvia a rubber isolator 36 (corresponds to an elastic member) by the cabinbracket 30 that extends to the left and right from the clutch housing11; and the support brackets 44 fixed to the lower end parts of thesupport frame 21 and positioned on the left and right sides of the rearpart are supported via a rubber isolator 46 (corresponds to an elasticmember) by a rear cabin bracket 45 that extends from a rear axle case47.

As shown in FIG. 4, the cabin bracket 30 is integrally formed by weldingtogether a fixing member 31 fixed to the clutch housing 11, a supportmember 32 for supporting the cabin 8 via the rubber isolator 36, areinforcing member 33 provided to the base of the cabin bracket 30, andan adjusting member 34 provided to the distal end part of the cabinbracket 30; and the cabin bracket 30 is fixed to the clutch housing 11by fastening and fixing the fixing member 31 to the clutch housing 11.

The rubber isolator 36 is composed of a cylindrical body 36 a throughwhich a connecting bolt 38 is inserted, a main isolator body 36 b madeof rubber, and a ring-shaped attachment fixture 36 c in which anattachment hole is formed. The rubber isolator 36 is fitted and insertedinto a rubber insertion hole 32 a formed in the support member 32, andthe attachment fixture 36 c is fastened and fixed to the support member32, whereby the rubber isolator 36 can be fixed to the cabin bracket 30.

Anti-vibration weights 40 are detachably attached to the distal end partof the cabin bracket 30, and the weight of the distal end part of thecabin bracket 30 can be adjusted by changing the number ofanti-vibration weights 40. For example, the characteristics of thevibration transmitted to the cabin 8 via the cabin bracket 30 can beadjusted according to the specifications or other characteristics of thecabin 8 or engine 4.

A bracket 41 is fixed to the lower surface of the floor panel 28 thatforms the lower end surface of the cabin frame 20, and a dish-shapedlinking member 37 is fixed on the lower surface of the bracket 41. Thelinking member 37 is brought into contact with the upper surface of therubber isolator 36, and the connecting bolt 38 is inserted into andfastened in the cylindrical body 36 a of the rubber isolator 36, wherebythe cabin 8 and the rubber isolator 36 can be connected, and the cabin 8can be elastically supported on the cabin bracket 30 via the rubberisolator 36.

A plurality of disk-shaped weights 35 is fastened together by theconnecting bolt 38 on the lower end of the cylindrical body 36 a of therubber isolator 36, and the characteristics of the vibration transmittedvia the cabin bracket 30 can be adjusted by changing the number ofweights 35.

A positioning pin 39 is fastened and fixed from below at the distal endpart of the cabin bracket 30, and the cabin 8 can be easily and rapidlypositioned in the forward-rear and left-right directions in relation tothe cabin bracket 30 by fitting the positioning pin 39 into apositioning hole 41 a provided to the bracket 41.

Such a configuration of the cabin bracket 30 makes it possible toenhance the rigidity of the cabin bracket 30 through the use of thereinforcing member 33 and the adjusting member 34. As a result,vibration from the clutch housing 11 can be transmitted to the cabin 8via the portions of the left and right center parts of the cabin bracket30 that have low rigidity and a low characteristic frequency, and thecharacteristic frequency of the cabin bracket 30 can be kept low whilethe strength of the cabin bracket 30 is maintained by the high rigidityprovided by the reinforcing member 33.

The anti-vibration weights 40 are mounted to the distal end part of thecabin bracket 30, and the weights 35 are mounted under the rubberisolator 36, whereby the characteristic frequency of the vibrationtransmitted to the cabin 8 via the cabin bracket 30 can be adjusted bythe anti-vibration weights 40 and the weights 35, and the characteristicfrequency of the vibration transmitted to the cabin 8 via the cabinbracket 30 and the rubber isolator 36 can be adjusted to a low value. Asa result, resonance and the like can be prevented from occurring insidethe cabin 8, and droning noise can be prevented from occurring.

[Detailed Structure of the Dynamic Damper]

The detailed structure of the dynamic damper 50 will be described basedon FIGS. 5 through 8. FIGS. 5 and 6 are a longitudinal sectional sideview and a longitudinal sectional back view, respectively, showing thevicinity of the dynamic damper 50 attached to the floor panel 28. FIG. 7is a back view showing the vicinity of the dynamic damper 50 attached toa rear wheel fender 29, and FIG. 8 is a longitudinal sectional side viewshowing the vicinity of the dynamic damper 50 attached to a supportbracket 44.

As shown in FIGS. 5 and 6, the dynamic damper 50 is composed of weightmembers 51, rubber isolators 52 as elastic bodies provided withviscosity and elasticity, cylindrical members 53, seating plates 54, andfixing bolts 56. The weight member 51 is composed of a flat bar made ofa steel plate, and two vertical attachment holes 51A are formed forfitting the rubber isolators 52. The rubber isolators 52 are made ofrubber that is set to a prescribed hardness, and are composed ofcylindrical main bodies 52A and flange parts 52B that are formed at theends of the main bodies 52A.

The cylindrical members 53 are composed of iron and steel pipematerials, and the length of the cylindrical members 53 in the verticaldirection is set so that the flange parts 52B at the tops of the rubberisolators 52 are mounted in a state of slight elastic deformation andcompression between the upper surface of the upper weight member 51 andthe lower surface of the floor panel 28 in a state in which the dynamicdamper 50 is mounted to the floor panel 28, and that the flange parts52B at the bottoms of the rubber isolators 52 are mounted in a state ofslight elastic deformation and compression between the upper surfaces ofthe seating plates 54 and the lower surface of the lower weight member51. As a result, the weight members 51 can be elastically supported bythe floor panel 28, and the weight members 51 can be prevented frombeing put out of vertical alignment by travel of the tractor or othereffects.

Through the elastic support of the weight members 51 by the floor panel28 via the rubber isolators 52 in this manner, vibration of the floorpanel 28 can be more efficiently reduced than in a case in which theweight members 51 is rigidly supported by the floor panel 28, forexample, and noise in the cabin 8 can be efficiently reduced. Adifferent configuration may also be adopted in which the weight members51 are elastically supported by the floor panel 28. For example, aconfiguration may be adopted in which the weight members 51 areelastically supported by the floor panel 28 through the use of springs(not shown), dampers (not shown), or other elastic bodies.

A configuration is adopted in which the upper surfaces and the lowersurfaces of the cylindrical members 53 are in contact with the lowersurface of the floor panel 28 and the upper surfaces of the seatingplates 54, respectively, and the dynamic damper 50 is fixed to the floorpanel 28. The tightening force of the fixing bolts 56 can be applied tothe floor panel 28, the cylindrical members 53, and the seating plates54. As a result, the fixing bolts 56 can be prevented from loosening dueto travel of the tractor and other effects, and the dynamic damper 50can be prevented from dropping out due to travel of the tractor andother effects.

The two weight members 51 are vertically stacked, a rubber isolator 52is fitted into the two attachment holes 51A from above the upper weightmember 51, and a rubber isolator 52 is fitted into the two attachmentholes 51A from below the lower weight member 51. The cylindrical members53 are then fitted into the main bodies 52A of the upper and lowerrubber isolators 52, the fixing bolts 56 are inserted so as to sandwichthe disk-shaped seating plates 54 and washers 55 from the lower side,and shouldered nuts 57 are fastened and fixed from the top, whereby theweight members 51 can be easily and rapidly attached to the floor panel28 via the rubber isolators 52.

The spaces between the external peripheral surfaces of the cylindricalmembers 53 and the internal peripheral surfaces of the rubber isolators52, and the spaces between the external peripheral surface of the mainbodies 52A of the rubber isolators 52 and the internal peripheralsurfaces of the attachment holes 51A of the weight members 51 are set soas to be small. As a result, the weight members 51 are prevented frommoving out of alignment in the planar direction through travel of thetractor and other effects.

As shown in FIG. 2, the dynamic dampers 50 are disposed along thefront-rear frames 15 fixed on the lower surface of the floor panel 28,so that the longitudinal direction of the dynamic dampers 50 is in thefront-rear direction, and the right-side dynamic damper 50 and theleft-side dynamic damper 50 are positioned slightly out of alignment inthe front-rear direction.

As shown in FIGS. 3 and 7, the dynamic dampers 50 are mounted to plates29B (which correspond to plate-shaped members) of the rear-wheel fenders29 positioned to the inside of the rear wheels 2. Two passage holes thatpass through in the left-right direction are formed in the front-rearframes 15 and the plates 29B; and the weight members 51, 51, the rubberisolators 52, 52, and the cylindrical members 53 that constitute thedynamic dampers 50 are fastened and fixed in the passage holes by thefixing bolts 56 and the shouldered nuts 57 via the seating plates 54 andthe washers 55.

A weight member 51 having the same shape as the abovementioned weightmembers 51 mounted to the floor panel 28 is mounted to the dynamicdampers 50 mounted to the rear-wheel fenders 29, allowing manufacturingcosts to be reduced and common parts to be used by employing the sameshape for the weight members 51. The detailed structure of the dynamicdampers 50 is the same as that of the above-mentioned dynamic damper 50mounted to the floor panel 28.

As shown in FIGS. 3 and 8, a dynamic damper 50 is mounted on the uppersurface of the support bracket 44 (which corresponds to a plate-shapedmember) for supporting the rear part of the cabin 8 on the rear cabinbracket 45 via the rubber isolator 46. A passage hole that passesthrough in the vertical direction is formed in the support bracket 44,and the weight member 51, the rubber isolators 52, 52; and thecylindrical member 53 that constitute the dynamic damper 50 are fastenedand fixed by a fixing bolt 56 and a shouldered nut 57 in the passagehole via seating plates 54 and a washer 55.

A single weight member 51 formed in a shape that conforms to the shapeof the support bracket 44 is mounted to the dynamic damper 50 mounted onthe support bracket 44, and the weight of the dynamic damper 50 is setso as to be approximately half the weight of the abovementioned dynamicdampers 50 that are mounted to the floor panel 28 and the rear-wheelfenders 29. The detailed structure of the dynamic damper 50 is the sameas that of the abovementioned dynamic damper 50 mounted to the floorpanel 28, except that the weight member 51, the rubber isolators 52, andthe cylindrical member 53 have different dimensions.

[Method for Setting the Attachment Positions of the Dynamic Dampers]

The method for setting the attachment positions of the dynamic dampers50 will be described based on FIGS. 9 and 10. FIG. 9 is a rough planview showing the method for setting the attachment positions of thedynamic dampers 50 on the floor panel 28; and FIG. 10 is a rough view inwhich the floor panel 28 or the like is modeled. In the descriptiongiven hereinafter, the method will be described for setting theattachment positions of the dynamic dampers 50 mounted to the floorpanel 28, but aspects of the method for setting the attachment positionsof the dynamic dampers 50 mounted to the rear-wheel fenders 29 and thesupport bracket 44 other than the difference in the components to whichthe dynamic dampers 50 are mounted are the same as in the case ofmounting to the floor panel 28.

As shown in FIG. 9, conditions that produce vibration (for example,conditions in which the engine 4 is at full throttle) are created, thevibration of the panel surface of the floor panel 28 within the rangessurrounded by the tilted lines in FIG. 9 are measured, and regions arespecified (specific frequency regions A) in which vibration occurs at aspecific frequency (e.g., 200 Hz) that easily causes noise inside thecabin 8 in the ranges surrounded by the thick lines in FIG. 9.

The center positions (A1 in FIG. 9) of the specific frequency regions Asurrounded by the thick lines in FIG. 9 are set as the attachmentpositions of the dynamic dampers 50. The regions in which vibrationoccurs at the specific frequency likely to cause noise inside the cabin8 are thus specified, and the positions for attaching the dynamicdampers 50 are set on the basis of the results of measuring thefrequency of vibration in the floor panel 28.

As described above, the dynamic dampers 50 in this tractor are mountedin positions along the front-rear frames 15 in positions near theregions A1 in FIG. 9 in the positional relationship with the front-rearframes 15.

As shown in FIG. 10A, when the floor panel 28 of the tractor is modeled,a beam fixed at both ends such as the one shown in FIG. 10A can beassumed. Vibration can be effectively reduced by mounting a dynamicdamper 50 in a position (near the maximum-amplitude portion L) ofsignificant vibration near the middle of the beam fixed at both ends.

When the support bracket 44 and the plates 29B of the rear-wheel fenders29, for example, are modeled, a beam fixed at one end, such as the oneshown in FIG. 10B, can be assumed, and the distal end parts of theplates 29B and the support bracket 44 correspond to the locations(locations near the maximum-amplitude portion L) of significantvibration.

As described above, the vibration of the panel surface of the floorpanel 28 is measured, and the specific frequency regions A are specifiedin which vibration at a specific frequency occurs, whereby the regionsof the panel surface of the floor panel 28 can be specified thatcorrespond to the maximum-amplitude portions L of the beam fixed at bothends shown in FIG. 10A. By mounting the dynamic dampers 50 in thepositions A1 of the centers of the specific frequency regions A, thevibration of the floor panel 28 can be effectively dampened by thedampening effects of the mass of the weight member 51 and the rubberisolators 52 that are provided with viscosity and elasticity.

The weight of the dynamic dampers 50 is set so that the dynamic dampers50 can effectively dampen the vibration of the floor panel 28 on thebasis of the results of a plurality of measurement in which the numberof weight members 51 is varied when a plurality of conditions isproduced in which the number or thickness of the weight members 51 ofthe dynamic dampers 50 in the abovementioned attachment positions isvaried, and vibration is generated.

[Results of Measuring Vibration Acceleration and Noise]

The results of measuring the vibration acceleration for each frequency,and the results of measuring the noise when the dynamic dampers 50 weremounted, will be described based on FIGS. 11 through 17. FIGS. 11, 13,and 15 are graphs comparing two types of data: data in which a vibrationpickup (not shown) was mounted in a position for measuring vibration (inthe case of the floor panel 28, for example, the A1 positions in FIG.9), the periphery of the position in which the vibration pickup wasmounted was struck by a hammer or the like (not shown) to generatevibration, and the vibration acceleration (G) for each frequency wasmeasured by the vibration pickup in a state in which a dynamic damper 50was attached to the floor panel 28 (FIG. 11), the rear-wheel fenders 29(FIG. 13), or the support bracket 44 (FIG. 15); and data in which avibration pickup was mounted in a position for measuring vibration, theperiphery of the position in which the vibration pickup was mounted wasstruck by a hammer or the like to generate vibration, and the vibrationacceleration (G) for each frequency was measured by the vibration pickupin a state in which the dynamic damper 50 was not attached.

FIGS. 12, 14, and 16 are graphs comparing two types of data: data inwhich the engine 4 was set to full throttle, and the noise (dBA) wasmeasured in the vicinity of the ears of the operator in the operatingseat 7 in a state in which the dynamic damper 50 was attached to thefloor panel 28 (FIG. 12), the rear-wheel fenders 29 (FIG. 14), or thesupport bracket 44 (FIG. 16); and data in which the engine 4 was set tofull throttle, and the noise (dBA) was measured in the vicinity of theears of the operator seated in the operating seat 7 in a state in whichthe dynamic damper 50 was not attached. In FIGS. 12, 14, and 16, thespectral values of the noise (dBA) for each ⅓ octave band in the Acharacteristic are indicated in the form of a bar graph for each ⅓octave band center frequency. “OA value” is an abbreviation for theoverall value, and is a value that is computed from the measured valueof the noise for each octave band and used for comprehensive evaluationof the noise.

FIG. 17 is a table comparing the spectral values and OA values of thenoise in cases in which the dynamic damper 50 is mounted to the floorpanel 28, the rear-wheel fenders 29, and the support bracket 44.

As shown in FIG. 11, when the dynamic damper 50 is mounted to the floorpanel 28, the frequency at the peak value of the vibration accelerationcan be moved from approximately 210 Hz (P1 in FIG. 11) to approximately170 Hz (P2 in FIG. 11), and the vibration acceleration of the floorpanel 28 near a frequency of 200 Hz can be kept low in comparison with acase in which the dynamic damper 50 is not mounted. As a result,vibration of the floor panel 28 near 200 Hz that easily causes noiseinside the cabin 8 can be kept low, and resonation of the floor panel 28can be suppressed.

As shown in FIG. 12, when the dynamic damper 50 is mounted to the floorpanel 28, the spectral value of the noise at a center frequency of 200Hz can be reduced approximately 6.7 dBA, and the OA value can be reducedapproximately 0.5 dBA in comparison with the case in which the dynamicdamper 50 is not mounted. As a result, noise near the ears of theoperator seated in the operating seat 7 can be reduced.

As shown in FIG. 13, when the dynamic damper 50 is mounted to therear-wheel fenders 29, the frequency at the peak value of the vibrationacceleration can be moved from approximately 125 Hz (P3 in FIG. 12) toapproximately 170 Hz (P4 in FIG. 12), and the vibration accelerationnear a frequency of 125 Hz can be kept low in comparison with the casein which the dynamic damper 50 is not mounted. The vibrationacceleration near a frequency of 200 Hz can also be kept low. As aresult, vibration of the rear-wheel fenders 29 near 125 Hz and 200 Hzthat easily causes noise inside the cabin 8 can be kept low, andresonation of the rear-wheel fenders 29 can be suppressed.

As shown in FIG. 14, when the dynamic damper 50 is mounted to therear-wheel fenders 29, the spectral value of the noise at a centerfrequency of 125 Hz can be reduced approximately 10 dBA, the spectralvalue of the noise at a center frequency of 200 Hz can be reducedapproximately 2.0 dBA, and the OA value can be reduced approximately 0.6dBA in comparison with the case in which the dynamic damper 50 is notmounted. As a result, noise near the ears of the operator seated in theoperating seat 7 can be reduced.

As shown in FIG. 15, when the dynamic damper 50 is mounted to thesupport bracket 44, the frequency at the peak value of the vibrationacceleration can be moved from approximately 400 Hz (P5 in FIG. 15) toapproximately 680 Hz (P6 in FIG. 15), and the vibration accelerationnear a frequency of 400 Hz can be kept low in comparison with the casein which the dynamic damper 50 is not mounted. As a result, vibration ofthe support bracket 44 near 400 Hz that easily causes noise inside thecabin 8 can be kept low, and resonation of the support bracket 44 can besuppressed.

As shown in FIG. 16, when the dynamic damper 50 is mounted to thesupport bracket 44, the spectral value of the noise at a centerfrequency of 400 Hz can be reduced approximately 4.4 dBA, and the OAvalue can be reduced approximately 0.4 dBA in comparison with the casein which the dynamic damper 50 is not mounted. As a result, noise nearthe ears of the operator seated in the operating seat 7 can be reduced.

As shown in FIG. 17, by mounting the dynamic damper 50 to the floorpanel 28, the rear-wheel fenders 29, and the support bracket 44, it ispossible to reduce the spectral values of noise at frequencies thateasily cause noise near the ears of the operator seated at the operatingseat 7 of the cabin 8 through the vibration of the floor panel 28, therear-wheel fenders 29, and the support bracket 44; and the OA value ofnoise near the ears of the operator seated in the operating seat 7 canbe reduced.

When the dynamic damper 50 is mounted to the floor panel 28, thespectral value of noise for which the center frequency is 200 Hz can besignificantly reduced, the spectral value of noise for which the centerfrequency is 125 Hz can be significantly reduced when the dynamic damper50 is mounted to the rear-wheel fenders 29, and the spectral value ofnoise for which the center frequency is 400 Hz can be significantlyreduced when the dynamic damper 50 is mounted to the support bracket 44.As a result, the spectral value of noise in a targeted frequency bandcan be effectively reduced, and the manifestation of these effects inthe OA value as a noise measurement result can be confirmed through themeasurement data.

It was also confirmed that noise-reducing effects in the cabin 8 weredemonstrated at different frequencies by the dynamic dampers 50 mountedto the floor panel 28, the rear-wheel fenders 29, and the supportbracket 44.

In FIGS. 11 through 17, measurement data for the vibration accelerationand noise were given by way of example in cases in which the dynamicdamper 50 was mounted to the floor panel 28, the rear-wheel fenders 29,or the support bracket 44, but noise inside the cabin 8 can be even moreeffectively reduced when dynamic dampers 50 are mounted in all or anytwo of the floor panel 28, the rear-wheel fenders 29, and the supportbracket 44.

In the previously described embodiment, an example was described inwhich the dynamic damper 50 (weight member 51) was attached to the floorpanel 28, the rear-wheel fenders 29, and the support bracket 44, but adynamic damper 50 (weight member 51) may be attached to a differentplate-shaped member constituting the cabin 8. For example, a dynamicdamper 50 (weight member 51) may be attached to the outer roof 27 oranother component. The position in which the dynamic damper 50 (weightmember 51) is attached to the floor panel 28 or other component may alsobe varied. For example, a dynamic damper 50 (weight member 51) may bemounted to a part on the external periphery of the operating seat 7 atthe rear of the floor panel 28.

In the previously described embodiment, an example was described inwhich the weight members 51 were attached to the floor panel 28, therear-wheel fenders 29, and the support bracket 44 via rubber isolators52, and were configured so as to function as dynamic dampers 50, but aconfiguration may easily be adopted in which weight members 51 are notattached via rubber isolators 52. Adopting such a configuration makes itpossible to simplify the attachment structure of the weight members 51and reduce manufacturing cost.

In the previously described embodiment, an example was described inwhich the weight members 51 were attached to the floor panel 28, therear-wheel fenders 29, and the support bracket 44 by fixing bolts 56,but a different method may also be employed for attaching the weightmembers 51 to the floor panel 28 and other components, and aconfiguration may be adopted in which rubber isolators 52 are bonded tothe weight members 51, for example, and the rubber isolators 52 bondedto the weight members 51 are bonded to the floor panel 28 and othercomponents. When the weight members 51 are not mounted via the rubberisolators 52, the weight members 51 may be welded to the floor panel 28and other components.

Embodiment 2

An embodiment relating to the acoustic absorbent material will next bedescribed.

[Overall Structure of the Tractor]

The overall structure of the tractor as an example of the vehicle with acabin will be described based on FIGS. 18 through 20. FIG. 18 is a sideview showing the entire tractor; and FIGS. 19 and 20 are a transversesectional plan view of the cabin 108, and a perspective view showing theleft rear part of the cabin 108 from the operating seat 107.

As shown in FIG. 18, the tractor is configured according to afour-wheel-drive specification in which a pair of left and right frontwheels 101 capable of steering and driving, as well as a pair of leftand right rear wheels 102 capable of driving, are provided to a vehiclebody 103. A hood part 105 in which an engine 104 and other componentsare housed is provided at the front of the vehicle body 103; and a cabin108 in which a steering handle 106, an operating seat 107, and othercomponents are housed is provided at the rear of the vehicle body 103. Aplurality of work lamps 109 is provided to the rear upper part of thecabin 108, and the work lamps 109 can illuminate the rear so thatcultivation or the like can be performed.

A main frame 110 extends forward from the lower part of the engine 104,and an axle case or the like (not shown) for mounting the front wheels101 is supported by the main frame 110. A clutch housing 111 extends tothe rear from the engine 104, a transmission case 112 positioned belowthe operating seat 107 is connected to the clutch housing 111, and thedrive force from the engine 104 is transmitted to the rear wheels 102.

A link mechanism 113 and a power take-off shaft 114 composed of a pairof left and right lift arms are provided at the rear of the vehicle body103; a rotary cultivator or the like (not shown) is connected to thelink mechanism 113 so as to be capable of being raised and lowered; andthe rotary cultivator or the like can be raised, lowered, and driven byconnecting the rotary cultivator or the like to the power take-off shaft114.

[Detailed Structure of the Cabin]

The cabin 108 is composed of a cabin frame 120, a front glass 116 forcovering the front surface of the cabin frame 120, doors 117 capable ofpivoting open and closed that are provided to the entrances on bothsides of the cabin frame 120, side glasses 118 provided to the rearparts of the doors 117, and a rear glass 119 for covering the rearsurface of the cabin frame 120. The cabin 108 is elastically supportedby a pair of left and right front cabin brackets 136 fixed to the leftand right sides of the clutch housing 111, and a pair of left and rightrear cabin brackets 137 that extend from the rear upper part of thetransmission case 112.

The cabin frame 120 is provided with an angled pipe support frame 121for supporting the cabin 108, and a lower frame 122 or the likeconnected to the support frame 121. The various frames constituting thecabin frame 120 are connected by welding and molding pipe materials orthe like.

A pair of left and right front pillars 123, a pair of left and rightcenter pillars CP, and a pair of left and right rear pillars 125 extendupward from the front end, the center part, and the rear end,respectively, of the lower frame 122; and the front pillars 123, thecenter pillars CP, and the rear pillars 125 are each connected to anupper frame 126.

The upper frame 126 is formed by welding and molding a front crossmember 127 having a bracket-shaped longitudinal sectional shape, a pairof left and right side members 128 having a bracket-shaped longitudinalsectional shape, and a rear cross member 129 having a bracket-shapedlongitudinal sectional shape, wherein an inner roof 133 is mounted tothe lower part of the upper frame 126, and an outer roof 134 is mountedso as to cover the upper frame 126 from above.

The rear cross member 129 is positioned at a height that is a prescribeddistance lower than the upper end parts of the left and right rearpillars 125, and a ventilation unit 135 is provided in the space formedbetween the rear cross member 129 and the outer roof 134.

The peripheral edge part of the inner roof 133 is mounted on the lowersurfaces of the front cross member 127, the left and right side members128, and the rear cross member 129; and the peripheral edge part of theouter roof 134 is supported by the upper surfaces of the front crossmember 127 and the left and right side members 128.

A floor panel 130 for forming the floor of the cabin 108 is connected tothe lower surface of the cabin frame 120; and rear-wheel fenders 132formed in a shape that covers the external peripheral parts of the rearwheels 102 from above are fixed to the left and right sides of the floorpanel 130. The floor panel 130 is provided with a step floor panel 130Aat the front of the cabin 108, and a sheet floor panel 130B at the rearof the cabin 108; and an operating seat 107 is provided in the center inthe left-right direction of the sheet floor panel 130B.

A front frame 131 extends upward from the step floor panel 130A in thecenter in the left-right direction of the front part of the cabin 108,and a steering handle 106 is supported on the front frame 131.

The front glass 116 is fixed across the left and right front pillars 123that form the cabin frame 120, and the front surface of the cabin frame120 is covered by the front glass 116. The rear glass 119 is attachedacross the left and right rear pillars 125 that form the cabin frame120, and the rear surface of the cabin frame 120 is covered by the rearglass 119.

The doors 117 are attached so as to be able to pivot open and closedabout the axes of the rear end parts in the entrances on both sides ofthe cabin frame 120 formed between the front pillars 123 and the centerpillars CP, and side glasses 118 are attached so as to be able to pivotopen and closed between the center pillars CP and the rear pillars 125.

[Detailed Structure of the Cabin Interior]

As shown in FIGS. 19 and 20, the operating seat 107 is provided in thecenter in the left-right direction of the rear part of the cabin 108,and an operating box 140 made of a resin is provided to the right of theoperating seat 107. A position lever 141 for controlling the raising andlowering position of the link mechanism 113, a power take-off selectionswitch 142 for switching the drive state of the power take-off shaft 114between an independent drive state and a state of synchrony with thetravel speed, an auto switch 43 for providing rolling control of theimplement and various other types of control, a cultivation depthsetting dial 144 for setting the cultivation depth of the implement, andother work controls are concentrated in the operating box 140.

A plurality of operating switches 145A for operating the ventilationunit 135 is provided to the operating box 140, and the force and othercharacteristics of the wind blown into the cabin 108 from theventilation unit 135 can be adjusted by operating the operating switches145A. A plurality of dial-type controls (not shown) is disposed within acover 146 provided to the operating box 140, and adjustment of therolling angle of the implement, and setting of the upper limit positionof the implement can be performed by dialing the controls.

A protective cover 147 made of a resin is provided to the left of theoperating seat 107, and the tops of the left and right rear-wheelfenders 132 are covered by the abovementioned resin operating box 140and the resin protective cover 147.

The front frame 131 that extends upward from the step floor panel 130Ais covered by a center cover 148, and the lower part of the steeringhandle 106 is covered by a handle cover 149.

Left and right ventilation ducts (not shown) extend forward between theouter roof 134 and the inner roof 133 from the left and right sides ofthe ventilation unit 135, and a plurality of air outlets is formed inthe left and right ventilation ducts. A plurality of outlet grilles 138capable of changing the direction of airflow from the ventilation ductsis provided to the inner roof 133, the air outlets of the ventilationducts are connected to the outlet grilles 138, and the air from theventilation unit 135 is blown in the direction adjusted by the operatorfrom the outlet grilles 138.

[Attachment Structure of the Acoustic Absorbent Material]

The attachment structure of the acoustic absorbent material 155 will bedescribed based on FIGS. 20 through 24. FIG. 21 is a longitudinalsectional front view showing the vicinity of the center pillar CP on theright side, and FIG. 22 is a transverse sectional plan view showing thevicinity of the center pillar CP. FIG. 23 is a detailed view showing theopenings portion 153 of the pillar cover 150, and FIG. 24 is aperspective view showing the rear part of the inner roof 133 as viewedfrom the operating seat 107. In FIGS. 20 through 23, the acousticabsorbent material 155 affixed to the pillar cover 150 on the right sideof the operating seat 107 is described as an example, but other aspectsof the acoustic absorbent material 155 affixed to the pillar cover 150on the left side of the operating seat 107 are the same except for thedifference in the left-right direction.

As shown in FIGS. 20 through 23, the center pillars CP are provided witha center pillar main body 124 and a pillar cover 150. The center pillarmain body 124 is formed so as to have a bracket-shaped transversesectional shape that opens toward the inside (towards the operating seat107), and cover attachment holes 124 a are formed in a plurality oflocations on the front surface and the back surface of the center pillarmain body 124.

The pillar covers 150 of the center pillars CP are made of resin andformed so as to have a bracket-shaped transverse sectional shape thatopens toward the outside. The covers are formed by integrally forming amain body panel 151 on the side of the operating seat 107 and front andrear side panels 152, 152, which are folded to the outside from thefront end and rear end of the main body panel 151.

The pillar cover 150 is molded to a round curved shape in which thecenter part of the main body panel 151 in the vertical direction curvesin towards the outside with a constant curvature as viewed from thefront, and noise near the ears of the operator seated in the operatingseat 107 can be efficiently absorbed by the acoustic absorbent material155 affixed to the inner surface 150A of the curved main body panel 151.The upper part and the lower part of the pillar cover 150 are molded inshapes that conform to the shapes of the inner roof 133 and theoperating box 140 at the bottom of the pillar cover 150, so as to createan attractive appearance as viewed from the operating seat 107.

An openings portion 153 that curves slightly inward towards the outsidein a vertically elongated rectangle shape as viewed from the inside isintegrally molded from the upper part to the lower part in the main bodypanel 151 of the pillar cover 150. A plurality of round hole openings153A is formed at equal intervals in the openings portion 153, andvertically adjacent openings 153A are arranged in a staggered state inthe horizontal direction so that the area (open area) occupied by theopenings 153A in the openings portion 153 can be kept large. All of theopenings 153A are preferably formed so as to have the same size, butsome of the openings 153A may be formed in a different size than otheropenings 153A. Each of the openings 153A preferably has a diameter of 1cm or less, and a diameter of 0.5 cm or less is more preferred.

Forming the openings portion 153 in which the openings 153A are providedin the pillar cover 150 in this manner makes it possible to maintain alarge open area of the openings portion 153 and to enhance thesound-absorbing effects of the acoustic absorbent material 155, as wellas to form the openings portion 153 without compromising aesthetics.

Forming the openings portion 153 in the pillar cover 150 makes it easyfor noise at the operating seat 107 to be transmitted to the acousticabsorbent material 155 affixed to the inner surface 150A of the pillarcover 150, and for sound to be absorbed into the acoustic absorbentmaterial 155. As a result, noise at the operating seat 107 can beefficiently absorbed by the acoustic absorbent material 155 incomparison with a case in which the acoustic absorbent material 155 isaffixed to the inner surface of a cover or the like (not shown) that isnot provided with the openings portion 153, for example.

Outwardly recessed front-rear indentations 151A, 51A are formed in thelower part of the main body panel 151 of the pillar cover 150, and worklamp operating switches 145B, 145B for switching the work lamps 109disposed in the upper rear part of the cabin 108 are provided in theindentations 151A, 51A.

Attachment holes are formed in a plurality of locations of the front andrear side panels 152, 152 of the pillar cover 150. Fixtures 154 aremounted in the attachment holes of the pillar cover 150, and when thepillar cover 150 is fitted in accordance with the positions of the coverattachment holes 124 a of the center pillar main body 124, and thefixtures 154 of the pillar cover 150 are pushed in towards the centerpillar main body 124, the distal ends of the fixtures 154 engage withthe cover attachment holes 124 a, and the pillar cover 150 can be fixedto the center pillar main body 124. When the fixtures 154 of the pillarcover 150 are pulled to the front or the rear, the engagement of thedistal ends of the fixtures 154 with the cover attachment holes 124 a isreleased, and the pillar cover 150 can be easily and rapidly removedfrom the center pillar main body 124.

A band-shaped acoustic absorbent material 155 that is elongated in thevertical direction is affixed to the inner surface 150A of the main bodypanel 151 of the pillar cover 150. The surface area of the acousticabsorbent material 155 is set so as to be larger than the surface areaof the openings portion 153 of the pillar cover 150, the acousticabsorbent material 155 is configured so as to be able to cover theentire area of the openings portion 153 of the pillar cover 150, and theexternal peripheral part of the acoustic absorbent material 155 isaffixed to the inner surface 150A of the pillar cover 150. The acousticabsorbent material 155 is preferably affixed using a publicly knownadhesive, but may also be attached by another publicly known method suchas bolts, nuts, or the like. Adopting a configuration in which theexternal peripheral part of the acoustic absorbent material 155 isaffixed to the inner surface 150A of the pillar cover 150 to fix theacoustic absorbent material 155 makes it possible to prevent theplacement of an adhesive or the like between the acoustic absorbentmaterial 155 and the inner surface 150A of the pillar cover 150, forexample, from adversely affecting the transmission of noise inside thecabin 108 to the acoustic absorbent material 155.

The acoustic absorbent material 155 is composed of a spongiform foammaterial made of a polyethylene-based material, and is configured sothat sound is absorbed and diffused into the acoustic absorbent material155, which is a porous material, whereby a portion of the sound energycan be converted to heat energy, and the sound can be absorbed. Throughthe absorption of noise inside the cabin 108, the heat energy isreleased from the openings 153A formed in the openings portion 153 whena portion of the sound energy is converted to heat energy, and the heatenergy of the acoustic absorbent material 155 can be efficientlytransferred.

As shown in FIG. 19, the center pillars CP are positioned to the leftand right of the head of the operator seated in the operating seat 107,and the surface of the acoustic absorbent material 155 is positioned soas to face towards the operating seat 107. The pillar cover 150 providedwith the acoustic absorbent material 155 can be positioned near the earsof the operator by thus attaching the pillar cover 150 provided with theacoustic absorbent material 155. As a result, the noise at the operatingseat 107 can be effectively absorbed by the acoustic absorbent material155 provided to the pillar cover 150, and noise that is unpleasant tothe ears of the operator can be effectively reduced.

The pillar cover 150 provided with the acoustic absorbent material 155is mounted to the vertically elongated center pillar main body 124. Notonly does this make it possible to effectively reduce noise that isunpleasant to the operator, but debris or dirt in the cabin 108 alsodoes not easily accumulate on the surface of the acoustic absorbentmaterial 155. As a result, the sound-absorbing effects of the acousticabsorbent material 155 can be sustained.

As shown in FIG. 22, a space is formed by the center pillar main body124 and the pillar cover 150 in the state in which the pillar cover 150is mounted to the center pillar main body 124, and the thickness andother characteristics of the acoustic absorbent material 155 are set sothat a prescribed space can be maintained to the outside of the acousticabsorbent material 155. As a result, the amplitude of the sound absorbedby the acoustic absorbent material 155 via the openings portion 153 ofthe pillar cover 150 is further reduced by the sound-wave-expandingeffects that occur when sound waves enter the space, and the noise atthe operating seat 107 can be even more efficiently reduced. The heatenergy of the acoustic absorbent material 155 can be efficientlydissipated by the space maintained to the outside of the acousticabsorbent material 155.

As shown in FIG. 24, a pair of left and right inside air supply vents133A in the shape of transverse elongated rectangles is formed in thecenter of the rear part of the inner roof 133, a resin mesh ventilationcover 139 is mounted to the inside air supply vents 133A, and the airinside the cabin 108 can be fed from the inside air supply vents 133A tothe ventilation unit 135.

Upper and lower openings portions 133B, 133B are formed in the innerroof 133 and are positioned above and below the inside air supply vents133A. An acoustic absorbent material 156 for covering substantially theentire area of the openings portions 133B is affixed to the innersurfaces (towards the ventilation unit 135) of the openings portions133B, and the acoustic absorbent material 156 has the same openingsformed therein as those of the openings portion 153 of theabovementioned pillar cover 150.

Forming the openings portions 133B in the inner roof 133 in positionsnear the inside air supply vents 133A in this manner makes it possibleto maintain a large open area for the openings portions 133B and toenhance the sound-absorbing effects of the acoustic absorbent material156, as well as to form the openings portions 133B without compromisingaesthetics.

The acoustic absorbent materials 156 provided to the inner roof 133 arepositioned at an angle above and to the rear of the head of the operatorseated in the operating seat 107, and the acoustic absorbent materials156 are arranged so that the surfaces thereof face towards the operatingseat 107. Attaching the acoustic absorbent materials 156 to the rearpart of the inner roof 133 in this manner makes it possible to positionthe acoustic absorbent materials 156 provided to the inner roof 133 nearthe ears of the operator. As a result, the noise at the operating seat107 can be effectively absorbed by the acoustic absorbent materials 156provided to the inner roof 133, and noise that is uncomfortable to theoperator can be effectively reduced.

Providing the acoustic absorbent materials 156 to the inner roof 133 notonly makes it possible to effectively reduce noise that is unpleasant tothe operator, but debris or dirt in the cabin 108 also does not easilyaccumulate on the surfaces of the acoustic absorbent materials 156. As aresult, the sound-absorbing effects of the acoustic absorbent materials156 can be sustained.

[Effects of Attaching the Acoustic Absorbent Material]

The results of measuring the noise near the ears of an operator seatedin the operating seat 107 of the cabin 108 in which the acousticabsorbent materials 155, 156 are attached will be described based onFIGS. 25, 26, and 29. FIG. 25 is a graph comparing two types of data:data in which the engine 104 was set to full-throttle, and the noisenear the ears of the operator of the operating seat 107 was measured bya noise meter (not shown) in a state in which the acoustic absorbentmaterial 155 and the acoustic absorbent material 156 were attached; anddata in which the engine 104 was set to full-throttle, and the noisenear the ears of the operator of the operating seat 107 was measured bya noise meter in a state in which the acoustic absorbent material 155and the acoustic absorbent material 156 were not attached.

In FIG. 25, the noise (dBA) for each ⅓ octave band in the Acharacteristic is indicated in the form of a bar graph for each ⅓ octaveband center frequency. “OA value” is an abbreviation for the overallvalue, and is a value that is computed from the measured value of thenoise for each octave band and used for comprehensive evaluation of thenoise.

FIG. 26 is a table comparing the spectral values and OA values at 800 Hzor higher of the noise in a case in which the acoustic absorbentmaterial 155 is mounted only to the center pillars CP, as well as a casein which the acoustic absorbent material 156 is mounted only to theinner roof 133, a case in which the acoustic absorbent material 155 andthe acoustic absorbent material 156 are mounted to the center pillars CPand the inner roof 133, and a case in which the acoustic absorbentmaterial 155 and the acoustic absorbent material 156 are not mounted,and a floor sheet 160 made of the same material as the acousticabsorbent material 155 is mounted to the lower part of the rear glass119 and the floor surface of the sheet floor panel 130B surrounded bythe tilted lines shown in FIG. 29. The measurement data obtained whenthe floor sheet 160 was mounted to the floor surface of the sheet floorpanel 130B and the lower part of the rear glass 119 are shown forcomparison, and have no bearing on the effects of the acoustic absorbentmaterial 155 and the acoustic absorbent material 156.

The spectral values of the noise in FIG. 26 were computed from valuesmeasured for each octave band when the measurement range of the noisemeter was set to 800 to 5000 Hz, and the OA values of the noise in FIGS.25 and 26 are values computed from values measured for each octave bandwhen the measurement range of the noise meter was set to 0 to 20000 Hz.

As shown in FIG. 25, when the acoustic absorbent material 155 and theacoustic absorbent material 156 were mounted, the noise at a centerfrequency of 800 Hz was reduced approximately 2.5 dBA, and the OA valuewas reduced approximately 0.7 dBA in comparison with the case in whichthe acoustic absorbent material 155 and the acoustic absorbent material156 were not mounted. As a result, the noise near the ears of theoperator seated in the operating seat 107 was reduced.

As shown in FIG. 26, when the acoustic absorbent material 155 wasmounted to the center pillars CP, the spectral value of the noise at 800Hz or higher was reduced 0.5 dBA, and the OA value of the noise near theears of the operator seated in the operating seat 107 was reduced 0.5dBA. Accordingly, mounting the acoustic absorbent material 155 to thecenter pillars CP made it possible to effectively reduce the noise nearthe ears of the operator seated in the operating seat 107 using a smallarea of the acoustic absorbent material 155.

Mounting the acoustic absorbent material 155 to the center pillars CP,and mounting the acoustic absorbent material 156 to the inner roof 133made it possible to reduce the spectral value of the noise at 800 Hz orhigher a further 0.2 dBA, and to reduce the noise near the ears of theoperator seated in the operating seat 107 a further 0.2 dBA.Accordingly, mounting the acoustic absorbent material 156 to the innerroof 133 made it possible to effectively further reduce the noise nearthe ears of the operator seated in the operating seat 107.

Mounting the acoustic absorbent material 155 to the center pillars CP,and mounting the acoustic absorbent material 156 to the inner roof 133made possible a 0.4 dBA reduction of the spectral value of the noise at800 Hz or higher, and a 0.4 dBA reduction of the OA value of the noisenear the ears of the operator seated in the operating seat 107 incomparison with the case in which the floor sheet 160 was mounted to thefloor surface of the sheet floor panel 130B and the lower part of therear glass 119.

As shown in FIG. 26, it can be confirmed that the spectral values and OAvalues of the noise were reduced by the same amounts, that there was nodifference between the OA values measured without limiting themeasurement range and the spectral values measured with a limitedmeasurement range by excluding the effects of solid borne sound ofapproximately 600 Hz or less transmitted through the cabin 108 byresonance of the floor panel 130 or other effects, and that thenoise-reducing effects of the acoustic absorbent materials 155, 156 weredemonstrated.

As a result, it was confirmed that the noise near the ears of theoperator seated in the operating seat 107 was effectively reduced by thesmall-area acoustic absorbent material 155 and acoustic absorbentmaterial 156 in comparison with the case such as the one shown in FIG.29, in which the large-area floor sheet 160 was mounted to the floorsurface of the sheet floor panel 130B and the lower part of the rearglass 119.

It was confirmed that when the acoustic absorbent material 155 wasmounted to the center pillars CP, the spectral value of the noise at 800Hz or higher was reduced 0.5 dBA, and the OA value was reduced 0.5 dBA,and the noise near the ears of the operator seated in the operating seat107 was reduced with particular effectiveness by the small-area acousticabsorbent material 155.

An example was described in the aforementioned embodiment in which roundhole openings 153A were formed in the inner roof 133 and the pillarcover 150 of the center pillars CP, but a different shape or structuremay be employed for the openings 153A. For example, slit-shaped openings153A as shown in FIG. 27A may be used, or mesh openings 153A as shown inFIG. 27B may be used.

An example was described in the aforementioned embodiment in which theopenings portion 153 was integrally molded in the inner roof 133 and thepillar cover 150 of the center pillars CP. However, for example, aconfiguration may be adopted in which an openings portion 153 fabricatedas a separate part is mounted to the pillar cover 150 as shown in FIG.28A, or a configuration may be adopted in which a openings portion 153fabricated as a separate part is mounted to the pillar cover 150, andthe acoustic absorbent material 155 is mounted to the inner surface 150A(inner surface of the openings portion 153) of the pillar cover 150, asshown in FIG. 28B.

An example was described in the aforementioned embodiment in which theopenings portion 153 was formed, and the acoustic absorbent material 155was mounted in the pillar cover 150 of the center pillars CP. However,for example, a configuration may be adopted in which the pillar cover150 is not provided, direct hole opening or another process is performedon the center pillar main body 124 composed of angled pipe to formopenings 124 b, and the center pillars CP are formed so that theacoustic absorbent material 155 is mounted to the inner surface 124A, asshown in FIG. 28C.

An example was described in the aforementioned embodiment in which theacoustic absorbent material 155 was affixed to the inner surface 150A ofthe pillar cover 150. However, for example, the acoustic absorbentmaterial 155 may be mounted in a position that is spaced a certaininterval apart from the inner surface 150A of the pillar cover 150 asshown in FIG. 28D, and the sound-absorbing effects of the acousticabsorbent material 155 can be further enhanced by forming the spacebetween the inner surface 150A and the acoustic absorbent material 155.The method for mounting the acoustic absorbent material 155 to the innersurface 150A of the pillar cover 150 is not limited to affixing, and adifferent mounting method may be used. For example, a method may beemployed for screw fastening using a pressure plate or the like (notshown).

An example was described in the aforementioned embodiment in which theopenings portion 153 was formed, and the acoustic absorbent material 155was mounted in the pillar cover 150 of the center pillars CP, but theopenings portion 153 may be formed and the acoustic absorbent material155 mounted in a different pillar. For example, an openings portion (notshown) may be formed and an acoustic absorbent material (not shown)mounted in the front pillars 123 or the rear pillars 125.

An example was described in the aforementioned embodiment in which theopenings portion 153 was formed, and the acoustic absorbent materials155, 156 mounted in the inner roof 133 and the pillar cover 150 of thecenter pillars CP, but an openings portion may be formed and an acousticabsorbent material mounted in an interior surface other than the centerpillars CP and the inner roof 133. For example, an openings portion (notshown) may be formed and an acoustic absorbent material (not shown)mounted in the operating box 140, the protective cover 147, the centercover 148, the handle cover 149, and other components. A configurationmay also be adopted in which a cover (not shown) besides that of theoperating box 140 and other existing interior parts is provided to thedead space inside the cabin 108 (e.g., the portion of the sheet floorpanel 130B around the operating seat 107), an openings portion is formedin the cover, and an acoustic absorbent material is mounted to the innersurface of the openings portion. Through such a configuration, noiseinside the cabin 108 can be reduced while effectively utilizing the deadspace inside the cabin 108 and not making modifications to the existinginterior parts.

An example was described in the aforementioned embodiment in which theopenings portion 153 was formed and the acoustic absorbent material 156mounted in the rear part of the inner roof 133, but the openings portion153 may be formed and the acoustic absorbent material 156 mounted in adifferent position of the inner roof 133. For example, forming anopenings portion 153 on the left and right sides of the center part inthe front-rear direction of the inner roof 133 and mounting the acousticabsorbent material 156 makes it possible to efficiently reduce the noiseto the left and right above the ears of the operator seated in theoperating seat 107.

An example was described in the aforementioned embodiment in which aspongiform foam material composed of a polyethylene-based material wasused as the acoustic absorbent material 155, but an acoustic absorbentmaterial composed of a different material may also be used. For example,an acoustic absorbent material composed of a polyether-based material ora felt-based material, or a urethane or other acoustic absorbentmaterial (not shown) may be used.

A tractor was described as an example of a vehicle with a cabin in thepresent specification, but the present invention may be applied in thesame manner to a different vehicle insofar as the vehicle has a cabin.For example, the present invention may be applied in the same manner toa combine or other agricultural work vehicle, a civil engineering workvehicle, a construction work vehicle, a passenger vehicle, or a truck orother commercial vehicle.

1-5. (canceled)
 6. A vehicle with a cabin, comprising: a vehicle bodythat is supported by a plurality of wheels and that supports the cabin;an openings portion in which a plurality of openings is formed and whichis provided to a portion of an inside surface of the cabin; and anacoustic absorbent material disposed on an inner surface of the insidesurface to which the openings portion is provided.
 7. The vehicle with acabin according to claim 6, wherein the openings portion is formed in apillar of a cabin frame that forms a part of the cabin.
 8. The vehiclewith a cabin according to claim 6, wherein the openings portion isformed at a rear part of an inner roof of the cabin.
 9. The vehicle witha cabin according to claim 6, wherein each of the plurality of openingshas a diameter of 5 mm or less, and vertically adjacent openings arehorizontally staggered from each other.
 10. The vehicle with a cabinaccording to claim 7, wherein the openings portion is formed in thepillar provided to a side of an operating seat provided inside thecabin.